A basic Liquid-Crystal Display (LCD) is structured in layers. An LCD has a mirror in back, which makes it reflective. Then, a piece of glass with a polarizing film on the bottom side and a common electrode plane made of indium-tin oxide on top is added. A common electrode plane covers the entire area of the LCD. Above that is a layer of liquid crystal substance. Next comes another piece of glass with an electrode on the bottom and, on top, another polarizing film disposed at a right angle to the first polarizing film.
The electrodes are hooked up to a power source. When there is no current applied, light entering through the front of the LCD will simply hit the mirror and bounce right back out. But when the power source supplies current to the electrodes, the liquid crystals between the common electrode plane and the electrode shaped like a rectangle untwist and block the light in that region from passing through. That makes the LCD show the display as a black color.
The pixels of an LCD that can show colors typically have three subpixels with red, green, and blue color filters to create each color pixel. Through the control and variation of the voltage applied to the subpixels, the intensity of each subpixel can range over multiple shades (e.g., 256 shades). Combining the subpixels produces a possible palette of many more (e.g., 16.8 million colors (256 shades of red×256 shades of green×256 shades of blue)).
LCD technology is constantly evolving. LCDs today employ several variations of liquid crystal technology, including super twisted nematics (STN), dual scan twisted nematics (DSTN), ferroelectric liquid crystal (FLC), and surface stabilized ferroelectric liquid crystal (SSFLC).
Furthermore, in general, light sources for providing light to the LCD are typically placed in one of two places. In some instances, along the edge of an LCD may be a cold cathode fluorescent (CCFL) or an array of light-emitting diodes (LEDs), forming what is often termed as an “edge-lit” LCD because the light is emitted into a side edge of a diffuser. In other instances, light sources may be arranged in an array or matrix behind the plane of the front of the display, forming what is often termed as a “back-lit” LCD because the light is emitted into the diffuser from a back surface of the display. In either case, using an optical system including a diffuser to spread out the light, these lights backlight the pixels of the display. Indeed, these lights are typically the only lights in the display.
The optical system includes a first sheet that makes a white background for the light. The next piece is called a “light-guide plate” (LGP) or coversheet. When light enters from the edge of the LGP in an edge-lit display, the light propagates through the length and width of the plate by total internal reflection, unless it hits one of many dots within the LGP. The dots make some of the light rays emerge out the front. Next, a diffuser film is added to help eliminate the dot pattern from the light-guide plate. After that a “prism film” may be added. This is used because light from the backlight emerges not only perpendicular to the back surface, but also at oblique angles. This prism film increases the perpendicularity of the light emission. Finally, another diffuser film may be added to try to help light the plane of the display surface evenly. Essentially, the purpose of the LGP, the prism film, and the diffuser films collectively is to function as a diffuser layer to spread the light emissions of the light sources in an attempt to make the light appear uniform across an entirety of the plane of the display surface, thus minimizing intensity of bright spots at the source point of the light emission.
Regardless of whether an LCD is edge-lit or back-lit, the size of the conventional LEDs used affects the thickness of the LCD, as well as the size of the diffuser needed to diffuse the light.
With regard to the size of the LEDs used in conventional displays, the end result is determined by fabrication and assembly processes according to conventional methods. In particular, the fabrication of the LED semiconductor devices typically involves an intricate manufacturing process with a myriad of steps. The end-product of the fabrication is a “packaged” semiconductor device. The “packaged” modifier refers to the enclosure and protective features built into the final product as well as the interface that enables the device in the package to be incorporated into an ultimate circuit. This packaging affects a thickness of the LEDs.
Notably, the conventional fabrication process for semiconductor devices starts with handling a semiconductor wafer. The wafer is diced into a multitude of “unpackaged” semiconductor devices, such as an LED. The “unpackaged” modifier refers to an unenclosed LED without protective features. Herein, unpackaged LEDs may be called “dies” for simplicity. In some instances, a thickness of the unpackaged LEDs may be 50 microns or less.